The present invention relates to a counterweight for use in a construction vehicle such as a hydraulic shovel and crane in which an implement is mounted on the front part of a revolving superstructure.
In a known construction machine such as a hydraulic shovel and movable crane, a counterweight is placed in the rear of a revolving superstructure to maintain a balance relative to the weight of load on the implement which is mounted on the front part of the revolving superstructure. Such a counterweight is indispensable but obstructive since it occupies much installation space, and therefore, there have been proposed many ideas for making use of the space of a counterweight.
With structural reductions in the space of the rear part of the machine body, several techniques have been proposed for giving various functions to parts of a counterweight in order to facilitate checking and maintenance of the peripheral devices of the engine. One example is disclosed in Japanese Utility Model Publication (KOKAI) No. 4-30151 (1992) which has a notch recess formed on the center portion of a counterweight for facilitating checking and maintenance of engine parts and a lid plate for covering the notch recess. When doing a check and maintenance, the lid plate is raised so that the worker can easily carry out work, utilizing the recess. Another example is disclosed in Japanese Utility Model Publication (KOKAI) No. 4-30152 (1992). According to this publication, the inner portion of the center of a counterweight is partially cut away to form a recess in which an auxiliary counterweight is embedded. This auxiliary counterweight is provided with a vent hole for interconnecting the inside and outside of the machine body thereby exhausting air from the engine to the outside of the machine through the vent hole.
Japanese Utility Model Publication (KOKAI) No. 61-17334 (1986) discloses a counterweight that can be split into front and rear portions. This counterweight is provided with a ventilation opening located at a position opposite to the engine and an exhaust silencer is put into the ventilation opening to reduce the exhaust noise of the engine.
Japanese Utility Model No. 2548492 discloses a counterweight part of which is provided with an exhaust duct thereby increasing the engine cooling effect as well as the noise eliminating effect.
Another example is proposed by Japanese Utility Model Publication (KOKOKU) No. 6-34438 (1994) according to which, a counterweight is divided into a center block and right and left blocks. In this counterweight, either the peripheral edge of the side face of the center block or the peripheral edge of the side face of the side block opposite to the peripheral edge of the center block is allowed to project and the other is recessed, such that the outer surfaces of the center and side blocks are connected to each other in a continuous fashion without a gap.
As described above, there have been already proposed various ideas for counterweights which are used in a construction vehicle composed of a lower traveling system and a revolving superstructure with an implement and are placed in the rear of the revolving superstructure. On the other hand, middle-sized and small-sized construction machines are recently widely used and the counterweights for such machines have to be placed near the center of rotation since these construction machines are required to make a small sharp turn and therefore have a small radius of turn. This reduces the installation space for the engine and its accessories mounted in the rear of the revolving superstructure, causing many troubles.
One of the above troubles is that since the counterweight is installed in the rear of the revolving superstructure so as to enclose the engine, leaving insufficient space, the workability of checking and maintenance of the engine, radiator and control valves such as the main pump becomes extremely poor. Therefore, the whole counterweight needs to be removed for carrying out checking and repair work (maintenance), so that much time is required when checking and repairing troubled parts in other locations (e.g., job sites) than repair shops.
The prior art arrangements described earlier are mostly associated with the construction machines having sufficient installation space for the counterweight. However, the above-described problem is outstanding in the case of middle-sized and small-sized machines of small-turn type which are required to install a counterweight in the proximity of the engine installing section.
In addition, for mounting a split counterweight in the rear of the revolving superstructure, its assembly structure must be simplified to facilitate assembly operation. However, the above-described prior art techniques do not pay much attention to the simplicity and safety of disassembly and assembly operations but only take into consideration the ease of maintenance achieved by disassembling or elegant design.
The present invention is directed to overcoming the foregoing problems and a primary object of the invention is therefore to provide a counterweight for use in a construction vehicle which allows a worker to safely easily carry out, from outside, checking and maintenance on parts such as an engine, while being in a natural pose without climbing on the counterweight.
The above object can be achieved by a counterweight for use in a construction vehicle according to the invention, which is used in a construction vehicle having a traveling vehicle body and a revolving superstructure with an implement, and wherein a region of the counterweight corresponding to the position of a part requiring maintenance is detachably formed.
In the above arrangement, the invention provides a counterweight for a construction vehicle which is designed to be partially dividable such that a region necessary for checking and maintenance can be detached. By virtue of this, when a check and repairs (corrective maintenance) are required for the engine or a similar part which is placed on the revolving superstructure, being ahead of the counterweight, the region of the counterweight corresponding to the position of the part can be detached so that the troubled portion of the part can be directly accessed from outside for repairing. With this arrangement, the worker is no longer required to disassemble and assemble devices, climbing on the counterweight and taking an awkward pose in a confined space, and as a result, the worker can quickly carry out repair work from the ground.
In the invention, the counterweight installed in the rear of the revolving superstructure is preferably provided with an opening which transversely penetrates through the counterweight. With such an opening that transversely penetrates through the counterweight at the position corresponding to the position of the engine and other parts disposed on the revolving superstructure, the troubled portion of the parts can be directly accessed from outside by bringing the opening into its open state. This increases workability and allows quick access when carrying out repair work, for instance, at a job site.
Preferably, the opening transversely penetrating through the counterweight is located on the central upper part of the counterweight and a separable sub-counterweight can be mounted on this opening from above so as to be detachable therefrom. With this arrangement, when there arises a need for a check and repairs for the engine section, the side of the engine section can be largely exposed by detaching the separable sub-counterweight so that the engine can be easily dealt with from outside. If the opening is defined at such a position that the worker faces the engine section through the opening when standing on the ground, the worker can carry out a check and repairs on the engine section in the most convenient pose only by bringing the opening into its open state, which brings about improved working efficiency.
It is preferable that the right and left corners of the counterweight be respectively provided with such an opening and separable sub-counterweights be detachably mounted on the openings located at these corners. When making a check and repairs on parts disposed in front of the aforesaid right and left corners, the parts facing the openings can be easily repaired from outside through the openings by detaching the separable sub-counterweights, similarly to the case of the opening defined at the center.
In the invention, the counterweight installed in the rear of the revolving superstructure is preferably designed such that an auxiliary sub-counterweight is detachably disposed on the inner side of the upper half portion of the central sub-counterweight located at the center and such that either or both of the right and left of the counterweight are provided with a separable sub-counterweight detachably formed. In this arrangement, the central sub-counterweight, the auxiliary sub-counterweight and the separable sub-counterweights can be adjusted to have substantially the same weight so that these sub-counterweights can be attached and detached with the same equipment (e.g., hoisting crane), resulting in easy operation.
It is preferable that the parting faces of the central sub-counterweight and separable sub-counterweight be provided with an engagement section. When this arrangement is employed in a small-turn type construction machine in which sufficient installation space is not left for the counterweight after installation of the engine and other devices in the rear of the revolving superstructure so that there is a difficulty in checking and maintenance of the engine and other devices, checking and maintenance of a troubled device can be easily carried out without interference by detaching a sub-counterweight which is located at the position corresponding to the position of the devices requiring repairs. Especially, detachment of a separable sub-counterweight enables the worker to work from outside in a convenient condition to treat the engine section and pumps installed in a minimum space and to carry out the work on the ground, so that improved working efficiency can be achieved.
The engagement section is a fitting section formed on the central sub-counterweight and separable sub-counterweight. This fitting section preferably has a gap and serves as a stopper as well at the time of detachment. The fitting section preferably comprises a projection on the parting face of a sub-counterweight working as a base and an engagement recess defined in the parting face of a sub-counterweight which fits to the parting face of the base sub-counterweight. The engagement recess is designed to be fitted on the projection and the parting faces are fastened by fasteners from outside.
In this arrangement, the counterweight has the fitting structure and is fixedly fastened by fasteners at its parting section, so that a separable sub-counterweight which is heavy in weight can be easily positioned at the time of attachment or detachment, by virtue of the gap between the projection formed on the parting face of the sub-counterweight which works as a base and the recess formed on the sub-counterweight which mates with the base sub-counterweight (the positions of the projection and the recess may be reversed). In the case of a small-turn type implement which does not have sufficient installation space for a counterweight, even if the separable sub-counterweight to be detached is shifted, by the distance corresponding to the gap, from a predetermined position relative to the parts attached to the revolving superstructure, one of the faces constituting the fitting structure that is for instance the face opposite to the projection functions as a stopper, so that the collision between the separable sub-counterweight and the parts positioned inside the sub-counterweight can be avoided and security can be ensured.
The central sub-counterweight and separable sub-counterweight have, at their lower portions, a common lower face plate used for maintenance of lower parts. While the conventional counterweight has a mounting section which is formed by extending the rear part of the revolving frame in order to attach a detachable cover to a position under the part requiring repairs and in the proximity of the counterweight mounting section, such a mounting part can be omitted from the counterweight of the invention thanks to the above arrangement so that the underside of the counterweight can be utilized. As a result, a simple structure can be obtained and the revolving frame can be simplified, leading to a reduction in weight as well as improved economy.